The present invention relates to a suspension system for a driver's compartment of a vehicle, more in particular, a suspension system including pneumatic springs.
Driving comfort optimization in vehicles, in particular, trucks with cabins suspended from the vehicle's chassis, has always been a point of attention. While most focus has been on optimizing passive suspension and adjusting the passive characteristics to vehicle and/or road conditions also, suspension systems have been proposed that minimize the disturbances relayed via the chassis by actively neutralizing the impact of road and/or vehicle disturbances in the cabin's suspension system. The aim is here to neutralize any disturbance in the cabin so that the suspension system holds the cabin virtually stable in a forced position countering roll, pitch or heave movements that occur in the vehicle due to accelerations. In addition, the cabin may be kept in a rest position with minimal impact deflection.
Such conventional active suspension systems experience difficulty in tuning and suffer from fairly high energy demand, which is a drawback in today's focus for energy economization.
While most of the active suspension utilize hydraulic pressure, in SAE technical paper series/,pap. 910023 1991 A. Wiesmeier, F. Uffelmann (IVECO Truck Engineering) “Vibration Isolated Cabin by Active Suspension-Requirements, Concept and First Results” a pneumatic setup is contemplated. The paper further details on a hydraulic suspension with a proportional valve arrangement for a suspended cabin configuration. A central pressure supply source is used to operate the pressure cylinders. A pneumatic setup was found unattractive in view of temperature and energy efficiency considerations. Indeed, Boyles thermodynamic gas law requires a complex physical model to be able to control the springs based on mass flow.
DE102009012581 nevertheless explores this direction and utilizes an inverted model of thermodynamic ground equations that is linearized over a control range to provide a controlled force in the pneumatic springs wherein a feed forward control is required for prediction of the required air mass in the pneumatic spring. A pneumatic proportional valve is contemplated to implement as a valve between a central pressure and the pneumatic springs. Importantly, it is contemplated that a proportional valve has a settable valve opening, dependent on a control voltage (or electric solenoid current).
WO 2010/019038 discloses a multipoint hydraulic suspension with an active and passive control mode.
The invention has as an object to provide a driver's compartment suspension with a valve control concept that is easily manufacturable and that has a smooth and high precision control of the gas pressure in the pneumatic springs, in order to neutralize road and/or vehicle disturbances in the driver's compartment and which provides for a robust and sufficiently durable design, specifically improvement of lifetime and pressure control accuracy.